import strutils
let
  n: int = stdin.readline.parseInt
  s: string = stdin.readline
var
  u, m, g: seq[int]
  ans: int = 0
for i in 0..<n:
  if s[i] == 'U':
    u.add(i)
  elif s[i] == 'M':
    m.add(i)
  else:
    g.add(i)
for i in u:
  for j in m:
    if g.find(2 * j - i) != -1:
      ans.inc
echo ans